Archaeologists on Orkney are facing a race against the elements to uncover a suspected 5,000-year-old tomb full of skulls found by a local digger.

Experts from the Orkney Research Centre are frantically attempting a rescue excavation on the mound, which has been badly damaged by JCB work.

The site was never thought to have been of archaeological interest until levelling work on the ground revealed large slabs and a network of chambers, causing a swift end to the development work.

Landowners used torches to spot waterlogged skulls inside a central passageway and a series of side cells in the mud.

Heavy rain and gale force winds have hampered their efforts to investigate the grave. In the first of a set of video updates planned for the rest of the two-week campaign, the Centre’s Dan Lee said the tomb could carry individual burial remains or “a jumble of bones”.

The Neolithic monument lies within striking distance of the Scottish island’s legendary Tomb of the Eagles visitor centre, a gruesome and compelling display of hands-on artefacts from a Bronze Age site found in 1958.

Orkney has been a consistent hotbed of tomb finds, following in the tradition of ancient burial rituals along the Atlantic coast.